Tehran, Iran — It’s a familiar political story: The presidential hopeful billed as the candidate of “prudence and hope” is facing withering criticism. His toughest opponents fear their longstanding grip on key power centers is waning irrevocably. They attack him harshly for failing to deliver on the economy and foreign policy – all in a bid to make him that most embarrassing of phenomena: a one-term president.

Iran’s election may not be for another eight months, but hard-line opponents of President Hassan Rouhani have already marshaled powerful tools to unseat him. They’re banking on a convergence of two key factors: public dismay over unrealized hopes for economic progress after the landmark nuclear deal, and their own desire for unity to ensure that a man they see as dangerously opening up Iran to the US and the West won’t remain in office.

But how far can Rouhani’s conservative rivals go to defeat him, using cash and hard-line media to amplify their already loud voices; and how big a challenge do they really pose?

Supporters argue that they will prevail: Rouhani has withstood excruciating pressure from his opponents, and faces no obvious contenders. They also point to the fact that conservative factions – often called “principlists” – have been defeated twice since 2013 at the polls by voters eager for greater social freedoms.

Yet his challengers see last year's nuclear deal, which dismantled part of Iran’s nuclear infrastructure, as capitulation to the United States. It's also viewed as an opening to interference in Iran’s affairs, including the deep-rooted business interests that are controlled by Iran’s Revolutionary Guard.

The fact that some US sanctions remain – and that banking restrictions still complicate transactions with Iran – means that many blame Rouhani for lack of economic progress. The approval Monday by the US Treasury Department of the sale of an initial 17 Airbus planes, with sales from Boeing expected to be approved in coming days, will be a boon.

For the president’s detractors and supporters alike, the stakes could not be higher for the 2017 vote.

“The 'principlists' will do everything to defeat Rouhani, so he loses the next election,” says Mojtaba Mousavi, founder of the conservative IransView.com website. “In the next 10 years the country will change very much. The leadership are old men, some may pass away, and no one knows what may happen. So it is very important for both sides, because this election will change the environment for the next decade.”

Rowdy crowd

Conservatives’ traction with some constituencies was on full display mid-summer, when Rouhani grew frustrated as he tried to address a crowd over the voices of protesters in Kermanshah, in northwest Iran. “You don’t listen to me and just keep repeating your slogans,” Rouhani scolded his audience, with an impatient wave of his hand amid a chorus of complaints about the economy.

Problems “cannot be done away with slogans, cannot be resolved with poems,” he said, calling on Iranians to “join hand in hand” to execute solutions.

Still, despite the array of tools at their disposal, Iran’s principlists face their own limits. The nuclear deal of July 2015, for example, was struck with the tacit support of Iran’s supreme leader Ayatollah Ali Khamenei.

And as a consummate insider since the first days of Iran’s 1979 Islamic revolution, Rouhani enjoys far closer ties and level of trust with Mr. Khamenei than Iran’s two previous presidents.

“The common word for [principlists] is ‘engineering.’ They want to engineer anything and everything,” says an Iranian analyst who asked not to be named. “They know too well they are in the minority and want to punch above their weight – and they are doing that.”

“They have been detonating [political] bombs and would love to end Mr. Rouhani’s career at the first term,” he says, noting a string of recent issues used to attack Rouhani, from the damaging release of pay slips of officials receiving vast salaries to complaints that joining the intergovernmental Financial Action Task Force to combat money-laundering amounts to buckling under the demands of arch-foe America.

The top attack line for Rouhani opponents is against overselling the positive impact of the nuclear deal – a tactic of raising hopes during two years of intensive negotiations that aimed to keep hard-line critics at bay inside Iran.

“Almost none of these promises were fulfilled. Now even many former supporters of Rouhani are critical of him,” says Hossein Shariatmadari, editor of the hard-line Kayhan newspaper, who is an official representative of Khamenei.

The negotiators “all admit the sanctions were only lifted on paper,” yielding “massive discontent,” he says. “The way the Americans are treating the Rouhani government is like waterboarding, the torture at Guantanamo.”

Rouhani has also been unable to always count on the supreme leader Khamenei’s support, despite his tacit backing of the nuclear deal.

Rouhani stated in July, for example, that the nuclear deal helped prevent an attack on Iran – something with which US Secretary of State John Kerry concurred. But Khamenei, in clear riposte to Rouhani, earlier this week dismissed any link to the nuclear deal. The “only” factor in removing the risk of war, he said, “has been and will continue to be military and defensive power.”

The popular view

Popular preferences are obvious, to some. Iranians took to the streets to celebrate Rouhani’s victory over a slate of conservative candidates in June 2013, and then when the nuclear deal was signed last year. In parliament elections in February, despite heavy vetting of reformist candidates and Rouhani allies, conservatives suffered a blow.

That vote “quite clearly showed the political taste of society,” say Davood Mohammadi, editor of the pro-Rouhani Iran newspaper. “People still preferred to vote for unknown candidates instead of known hardliners. Not one conservative won a seat in Tehran.”

“Lack of contentment in people does not mean people are anti-Rouhani,” says Mr. Mohammadi. “While hardliners are going the extra mile to highlight the failures, most people know they are the legacy of Mr. Ahmadinejad.”

Yet opponents of Rouhani make different calculations about their chances, and their popularity.

“Rouhani is suffering this fear that he will not be reelected, and he is showing it,” says Mikaeel Dayyani, the leader of a student group of basiji, a volunteer militia known for rigorous religious training, referring to Rouhani’s Kermanshah speech.

“It was the nuclear deal that helped him move forward…. But one year [later] the [high] is over,” and Rouhani’s votes “are collapsing very much, day by day,” he suggests.

“I don’t claim we will be able to win and make him one-term,” says Mr. Dayyani. “But what I can say for sure is that Rouhani’s position is very fragile.”

Yet that fragility may not translate into a new president next spring.

“For us it’s very important to know that when a hardliner says, ‘Rouhani is failing’ – and he is failing on some things – what is on the horizon? What is the alternative? There is no one else,” says an Iranian analyst who asked not to be named.

“We are all going to elect Rouhani again, but the real problem is bigger,” she insists. “We will vote again, but there is a deep cleavage between the people and the Islamic Republic.”